import numpy as np
import math
import matplotlib.pyplot as plt


fig  = plt.figure()
ax = fig.add_subplot(1,1,1)

d = 500
divisor = 0.06
t_def = [i for i in range(-d,d)]
t_rate = []
for _def in t_def:
    t_rate.append(1 - divisor * _def / (1 + (divisor * abs(_def))))
ax.plot(t_def,t_rate)


plt.show()
